1. Field of the Invention
The present invention relates to a thin plate supporting container for housing, storing, and transporting thin plates such as semiconductor wafers, storage disks, or liquid crystal glass substrates.
2. Related Background Art
A thin plate supporting container is generally constructed by a container body and a lid unit for closing the upper opening of the container body. In the container body, slotted plates are provided on opposite side walls, and a plurality of thin plates such as semiconductor wafers are supported between the slotted plates.
The slotted plates are detachably supported in the container body. Specifically, a supporting hole is provided in the slotted plate side and a supporting projection is provided on the container body. By the mating of the supporting hole and the supporting projection, the slotted plates are detachably supported in the container body As disclosed, for example, in International Publication WO99/39994 wherein sets, each consisting of the supporting hole and the supporting projection, are provided in three positions. Since sets of the supporting hole and the supporting projection are provided in three positions, the slotted plate is not deflected. Provision of sets in only two positions, i.e. at opposing ends of the slotted plate is also possible. In this latter case, however, since the supporting hole and the supporting projection have a circular shape and can rotate in a state where they are fitted with each other, the slotted plates may be deflected.
Further, since the slotted plate is positioned by the supporting hole and the supporting projection, the deepest portion of the slotted plate may slightly deviate. When the thin plate supporting container is disposed longitudinally, semiconductor wafers are supported in the deep portions of the slotted plates and, if there is a positional deviation in the deep portions of the slotted plates, the positions of semiconductor wafers will deviate in the thin plate supporting container.
A plurality of plate segments forming the slotted plate curve along the periphery of a semiconductor wafer close to an inlet/outlet port. Because the inlet/outlet port side of a plate piece extends toward the semiconductor wafer, there is a high possibility that a semiconductor wafer supplied/taken out will come into contact with the plate segment. To solve the problem, the inlet/outlet port side of the plate piece must be widened toward the container body. In this case, however, the semiconductor wafer supporting positions are at the innermost end and at an intermediate position. There is no support near the inlet/outlet port, so that the support is unstable.
Between the semiconductor wafers and the bottom of the thin plate supporting container, a sufficient gap is provided to prevent the semiconductor wafers from coming into contact with the bottom in case of an abnormal shock, in the case of a fall or the like. To provide such a gap, however, the thin plate supporting container must be taller. When the thin plate supporting container is packed in a box, the gap between the bottom of the box and the bottom of the thin plate supporting container is small. Accordingly, the amount of cushioning which can be put between the bottom of the box and the bottom of the thin plate container is small. Although there is no problem in normal transportation, in case of an abnormal shock due to a fall or the like, the small amount of the cushioning poses a problem. It is preferable that the amount of cushioning be larger.
A top flange and a handle are detachably attached to the thin plate supporting container. When a strong external force tending to pull off the top flange or handle is created by an abnormal shock due to fall of the thin plate supporting container or the like, there is the possibility that a locking pawl or the like will come off and the top flange will detach.
There is also the possibility that a known latch mechanism for fixing a lid unit to the container body will be caught by the container body when the latch mechanism is unlatched to detach the lid unit.
On the interior side of the lid unit, a thin plate pressing member is provided. Fitting grooves are formed in the thin plate pressing member. Semiconductor wafers are fitted into the fitting grooves and thereby individually supported. The fitting groove is formed in a V shape, the angle of the V-shaped fitting groove is usually an obtuse angle, and the periphery of a semiconductor wafer is lightly caught in the fitting groove. Although there is no problem in normal use, an abnormal shock may cause the semiconductor wafers to turn or be displaced.
The thin plate pressing member is formed of a number of pressing bands disposed in parallel for supporting the semiconductor wafers separately at predetermined intervals, with the periphery of a semiconductor wafer supported by being fit in a fitting groove formed in the pressing band. In this case, if a semiconductor wafer comes out of the fitting groove in the pressing band, the semiconductor wafer may enter a gap between the pressing bands.
On the bottom of the container body are transversely oriented positioning means for positioning the thin plate supporting container. The positioning means is constructed by three fitting grooves provided at almost equal intervals. When positioning projections on a base stand side lodge in the fitting grooves, the container body is accurately positioned. Since the fitting grooves are made of the same material as that of the thin plate supporting container, in entering the fitting grooves, the positioning projections do not slide smoothly. There is the possibility that the positioning projection will stop midway in the fitting groove and accurate positioning will not be achieved.